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FXUS63 KGRB 161139
AFDGRB
Area Forecast Discussion
National Weather Service Green Bay WI
539 AM CST Fri Feb 16 2018
Updated aviation portion for 12Z TAF issuance
.SHORT TERM...Today...Tonight...and Saturday
Issued at 333 AM CST Fri Feb 16 2018
Lingering flurries will end over eastern WI within the next
couple hours, as a short-wave trof moves through. In addition,
lake effect snow showers should taper off over far northern WI as
low-level winds become westerly. Clearing skies will spread east
across the forecast area early this morning, and temperatures will
drop off quickly as this occurs.
A ridge of high pressure will bring mostly sunny skies today.
Temperatures will be much cooler than the past two days, with
highs only reaching into the upper teens to middle 20s.
The surface ridge will slide east tonight, with increasing
southwest winds causing WAA to develop. A 40 knot LLJ will take
aim on north central and central WI late tonight, with enough
saturation occurring for scattered light snow showers or flurries
to develop. The snow showers/flurries will overspread the rest of
the region Saturday morning, and continue into the afternoon as a
cold front arrives. Snow accumulations will be light and less than
an inch in most locations. Lows tonight should range from the
single digits northwest to the lower teens southeast. Highs on
Saturday should warm into the upper 20s and lower 30s.
.LONG TERM...Saturday Night Through Thursday
Issued at 333 AM CST Fri Feb 16 2018
Forecast concerns mainly revolve around model trends for wintry
precip during the Sunday through Tuesday time period. Looking at
the latest model solutions, the ecmwf remains on the northern edge
of guidance in terms of frontal placements, while the gfs is
positioned between the ecmwf and gfs ensemble mean. Without a clear
model preference, will use a blend of the ecmwf and gfs for Sunday
and Sunday night, then transition to the gfs which appears to be
more in the middle of the range of solutions.
Saturday night through Sunday night...Any lingering light snow will
be exiting eastern Wisconsin early in the evening with the departure
of the shortwave. Will see partial clearing occur from west to east
behind the system for late Saturday night, but clouds will quickly
advance into the region ahead of the next low pressure system and
developing warm front over the northern Plains. The next area of
precip is expected to quickly move into northern WI north of the
warm front on Sunday morning and possibly continue into the evening.
Most of the snow should remain north of the highway 29, with the
highest amounts of 2-4 inches near the U.P. border. Would not be
surprising to see some freezing drizzle mix in with the snow as the
main area of snow exits, but not confident in this sort of detail
just yet. Highs on Sunday will remain mild and range from the mid
20s in the north to mid 30s in the south.
Rest of the forecast...Precipitation is expected to become more
widespread on Monday when a cold front moves across the area, with a
wave of low pressure traveling northeast along it into Monday night.
Position of the front will be critical in determining where various
precip types will fall. Warm air aloft will be surging into central
and northeast WI during this time, which sets up a scenario where
heavy snow could fall across the north, rain could fall in east-
central WI, and a wintry mix (sleet/freezing rain) corridor could
set up in-between. All this said, confidence of frontal locations
is relatively low, so locations, timing, and amounts could certainly
change over the next few days. Though the bulk of the precip will
fall during the Monday and Monday night time period, light precip is
likely to continue into Tuesday afternoon or Tuesday night. This
system will likely have a large impact on the region. Arctic high
pressure will then build into the region for Wednesday into Thursday.
&&
.AVIATION...for 12Z TAF Issuance
Issued at 529 AM CST Fri Feb 16 2018
Stratocumulus with bases of 2500-4000 feet AGL will exit eastern
WI by 14z-15z, followed by clear skies through this evening.
Clouds will thicken over parts of north central and central WI
late tonight, with scattered light snow showers or flurries
arriving toward daybreak.
The main aviation concern will be LLWS, which will develop in
north central WI late this evening, then spread southeast
through the overnight hours. Southwest winds will increase to
40 to 45 knots just above the surface.
&&
.GRB WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM.....Kieckbusch
LONG TERM......MPC
AVIATION.......Kieckbusch